The present invention generally relates to the field of measurement devices and more particularly to those directed toward measuring ultraviolet radiation. It is well known in the scientific community that ultraviolet radiation has the distinctive ability to cut electrons from an atom or molecule, thereby creating an electric charge. The amount of free electrons and total electric charge generated by ultraviolet radiation is proportional to the amount or quanta and total energy of the ultraviolet radiation applied to the object in which the electric charge is generated. The process of generating an electric charge via the exposure of an object to ultraviolet radiation does not require any external energy, a battery , or power supply, but rather requires only the ultraviolet radiation itself.
The process of cutting an electron from an atom or molecule is extremely fast, and usually less than about 10−13 seconds. Accordingly, an electric charge may be created by continuous ultraviolet radiation, as well as by pulsed ultraviolet radiation. The value of the electric charge generated by the ultraviolet radiation is generally very small, and sometimes almost unmeasurable. However, with very high intensities of ultraviolet radiation as are typically employed in industrial applications, such high intensities allow the electric charge created by the ultraviolet radiation to be measured, thus allowing for the dose of the ultraviolet radiation applied to an irradiated object to be measured.
Ultraviolet radiation measuring devices (often referred to as “radiometers and dosimeters”) are frequently used in various industries, including the optical lens industry, the ultraviolet curing industry, and the ultraviolet photolithography and printing industry. Prior art ultraviolet radiation measuring devices typically include a sensor for producing an electrical signal under the influence of ultraviolet radiation, and a display for showing the value of the ultraviolet radiation level. In addition to the sensor and display, these prior art devices include electronic circuitry which is used to convert the electrical signal produced by the sensor from the exposure thereof to the ultraviolet radiation to a form that is presentable on the display. Such electronic circuitry typically includes integrating and amplifying units, as well as other electronic components. Subsequent to the electronic integration of the signal, this “sample and hold” electronic circuitry is operable to present on the display a measured dose of the ultraviolet radiation applied to the sensor, as well as a peak intensity of the ultraviolet radiation.
However, in the prior art ultraviolet radiation measuring devices, the sensor, as well as other electronic components of the electronic circuitry, require electric power for the proper operation thereof. As such, the prior art measuring devices must also be provided with internal and/or external power supplies to provide electrical power to both the sensor and electronic circuitry thereof. Additionally, such prior art measuring devices are typically very complex in construction, and susceptible to failure due to the relative complexity of the electronic circuitry therein.
In U.S. Pat. No. 6,144,036 previously issued to Applicant and incorporated herein by reference, an ultraviolet radiation dosimeter is disclosed which generally measures dosage levels of ultraviolet radiation from an ultraviolet radiation source. However, improvements have been discovered which fulfill a need in the industry for an ultraviolet radiation dosimeter which is compatible with existing ultraviolet radiation source devices, able to measure intensity levels continuously, and able to receive measurement data from multiple light guides, including those from existing ultraviolet radiation source devices.
In this regard, it has been discovered that it is desirable to measure the rate of forming an electric charge, or intensity level, from the ultraviolet radiation source. More specifically, ultraviolet radiation sources use lamps and/or bulbs which have an unpredictable life expectancy. Over time, the lamps may degrade and generally provide a decreased intensity when compared with a new lamp or one which is capable of providing ultraviolet radiation at full strength. It is generally difficult to determine when replacement is necessary unless the amount of ultraviolet radiation emitting from the lamp is measured. Disadvantageously, lower than expected ultraviolet radiation emitted from the lamp may cause the irradiation target to be irradiated for an improper length of time. However, by measuring the intensity level of such ultraviolet radiation, the lamp and associated reflectors can be replaced at precisely the proper time to thereby ensure uninterrupted use of the lamp.
Additionally, during ultraviolet radiation spot curing, fluctuations in AC line voltage, ambient temperature and humidity may cause the power supplied to the ultraviolet radiation source to be adversely affected. For example, power can vary under the influence of these factors by as much as up to plus or minus 50% in any given day. In providing a ultraviolet radiation device which measures the intensity level of the ultraviolet radiation emitted therefrom, such adverse effects on available power may be compensated for by altering and controlling the ultraviolet radiation exposure time.
Additionally, while several prior art dosimeters and ultraviolet light source devices are available, such devices generally fail to provide a simplified measurement device which includes built-in light guides or has the ability to receive external light guides from existing ultraviolet light source devices while measuring ultraviolet radiation being irradiated at a target. While some combination devices exist which integrate proprietary dosimeters into the ultraviolet radiation source devices, such dosimeters are specifically designed to calibrate and measure the ultraviolet radiation being emitted from its own light guide, not that of other ultraviolet radiation source devices.
It is also desirable to determine such intensity level measurements during spot curing and other applications without interrupting such processes. In particular, it has been discovered that unpredictable results sometimes occur during spot curing where the actual ultraviolet radiation being emitted from an ultraviolet radiation source is inaccurate with respect to the expected ultraviolet radiation dosage and intensity levels. An operator recognizing this inaccuracy typically must disconnect the ultraviolet radiation source from the irradiation target and to measure the actual ultraviolet radiation. As previously described, such inaccuracies may result from a degraded lamp. As a result, uneven or inaccurate spot curing may occur since disconnection of the ultraviolet radiation source from the initially irradiated location requires realignment of the ultraviolet radiation source with that precise location. Such precision is often not achieved and the irradiated target generally becomes irregularly cured with some areas being exposed to too much ultraviolet radiation while other areas are exposed with too little ultraviolet radiation. Additionally, disconnection of the ultraviolet radiation source from the irradiation target may cause additional inaccurate curing since the operator must approximate remaining exposure time required after disconnection.
Thus, it is desirable to monitor the intensity level of the ultraviolet radiation source so as to determine whether irradiation exposure time should be adjusted due to a degradation in the lamp's intensity level, power fluctuations, and to be able to do so with a device which is compatible with existing ultraviolet radiation source devices. The prior art generally fails to provide such measurements on the rate of charging and/or intensity of the ultraviolet radiation source without requiring interruption of irradiation, and further fails to provide measurement devices which may receive existing light guides from ultraviolet radiation source devices. The present invention addresses these deficiencies by providing an ultraviolet radiation measurement device which may obtain a dosage level and an intensity level of an existing ultraviolet radiation source during irradiation of a target without interruption.